Pulse counting magnetic apparatus



April 4, 1967 w, GORE ETAL PULSE coun'rme MAGNETIC APPARATUS Filed Oct. 14, 1963 FIG.1

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I'NVENTFORS GERHA RD w. GORE couu GREEN AGENT United States Patent 3,312,830 PULSE COUNTING MAGNETIC APPARATUS Gerhard Werner Gore, Parley, Surrey, and Colin Green, Horsham, Surrey, England, assignors to North American Philips Company, Inc., New York, N.Y., a corporation of Delaware Filed Oct. 14, 1963, Ser. No. 315,893 7 Claims. (Cl. 307--88) This invention relates to electric retarding devices, that is to say devices of the kind which supply an output signal after a predetermined time, for example one minute, after a control signal is applied to it.

Such devices are used inter alia in the domain of railway signalling. The case may then arise, for example, that an operator has set a signal to safe and then notices that the track switch is not in the correct position. He must in this case not immediately change over the track switch because there would be a chance of the switch being changed over under a train which is just passing and this could naturally give rise to serious accidents. Consequently he must first set the signal to danger, whereafter the switch may be changed over only after a period such that it is certain that the train either has come to a standstill before the signal, or has already passed the switch, in other words the switch must remain blocked during this period under the control of the retarding device. It will be evident that such retarding devices must be extremely reliable in operation under any conditions and hence must have a fail safe character, that is to say if a fault occurs somewhere a condition must arise such that accidents cannot happen.

A retarding device according to the invention comprises a known pulse counting circuit including a core of magnetic material having a rectangular hysteresis loop, means being provided for setting the core to a determined rest state of remanence and also means for applying clock pulses to a first winding on the core and an output impedance connected in series with it, from which the output signal may be derived so that the impedance of the winding normally is comparatively high relative to the output impedance until the core is controlled into its saturation area.

The electric retarding device according to the invention is characterized in that means are provided for producing a premagnetization for setting the core to the defined rest condition and that the control signal is applied to a second winding on the core with a polarity and an amplitude such that the premagnetization is neutralized, the clock pulses being applied to the first winding through a gate circuit which is controlled by the signal current flowing through the second winding so that the gate is open only in the presence of the signal current.

In order that the invention may be readily carried into effect, it will now be described in detail, by way of example, with reference to the accompanying diagrammatic drawing in which:

FIG. 1 shows one embodiment of a retarding device according to the invention;

FIG. 2 shows an example of a hysteresis loop of the magnetic core used in this device.

The retarding device shown in FIG. 1 comprises a core 10 of magnetic material having a rectangular hysteresis loop, for example as shown in FIG. 2. Three windings 11, 12 and 13 are provided on the core 10.

An auxiliary current 111 is supplied by a source (not v shown) through a conductor 18 to the winding 12 so that the magnetization of the core 10 is normally adjusted at point A of the curve in FIG. 2. The control signal is applied through a conductor 20 and a gate to the winding 13. The winding sense of the windings 12 and 13 and the polarity and strength of the currents Ib and Is flowing through said windings are so chosen that the whole premagnetization of the core it brought about by the auxiliary current I!) is neutralized when the signal is pres ent on the conductor 20. The gate 15 is controlled by the auxiliary current lb so that the gate 15 passes the signal current only if the auxiliary current is present.

Clock pulses Ic may be supplied by a pulse generator (not shown) through a conductor 23 and a gate 16 to the winding 11 on the core 10. The gate 16 is controlled by the signal current Is flowing through the winding 13 so that the gate normally is cut off and hence does not pass clock pulses and becomes conducting when the current Is is present.

A winding 24 of an output transformer 25 is connected in series with the winding 11, whilst the output signal may be derived from a winding 26 on transformer 25.

The device operates as follows:

So long as there is no signal on the conductor 29, the gate 15 is cut ott and the magnetization of the core 10 is adjusted to point A of the hysteresis curve of FIG. 2. When a signal is applied the current is eliminates the premagnetization, as previously stated, so that now in the first instance the magnetization is adjusted to point C of the curve of FIG. 2, while the gate in becomes actuated and transmits the clock pulses lc with a duration R and a constant voltage amplitude V to the winding 11. The magnetic inductance of the core is varied in a stepwise manner under the control of said pulses, that is to say by the first pulse from point C through a to b, by the second pulse from b through a and c to d, by the third pulse from a through c and e to 7, etc. In fact, according to the induction law, there applies that the inducted electromotive force produced in the winding 111 is proportional to the variation in the magnetic flux per unit time that passes through the winding 11. If the impedance of the winding 24- on transformer 25 is small enough said inducted electromotive force is equal to the voltage V of the clock pulses applied through the gate 16. If, furthermore, the core It) has a cross-section A, the number of turns of the winding 11 is N and the magnetic inductance is B, the flux occurring is NAB.

During each pulse, a variation AB thus occurs in the inductance B which is equal to Alarm wherein T is the duration of each clock pulse. As pre viously mentioned, the inductance B will thus increase in a stepwise manner (the distances C to b, b to d, d to 1, etc. in FIG. 2 being equal to AB) until point D is reached. The core is then saturated and no further variation in the inductance B occurs, which also implies that the impedance of the winding 11, which showed a certain self inductance during the variation in inductance, falls off to a very low value and the clock pulses are now applied to the winding 24, this resulting in an output signal voltage at the winding 26.

The total variation of the inductance between points C and D is equal to B so that the number of pulses required for bringing about said variation is equal to B /AB.

The delay time, that is to say the time which elapses after the control signal is applied to the conductor 20 until the output pulses appear on the winding 26, is adjustable to any value desired by suitable choice of the number of clock pulses per second, for example 1 per second, and of the number of turns of the winding 11.

When the control signal is switched off again, the gate 16 is cut off and the magnetizations of the core 10 will be readjusted to point A by the action of the auxiliary current Ib, that is to say the action of the control signal 3 is wholly eliminated and for a succeeding delay period there is started from a well-defined magnetic condition.

If, however, no auxiliary current would flow through the winding 12 for some reason or other the resetting of the core to the rest condition would not be guaranteed. However, in this case, the control signal cannot become active and initiate a delay period since the gate 15 is cut off. Consequently, no current can flow through the winding 13 and the gate 16 remains cut off so that no clock pulses are transmitted.

The currents supplied to the windings 12 and 13 need not fundamentally be direct currents, but may also be formed by pulses which are relatively synchronized, which may afford advantages under certain conditions. The frequency of such pulses may be equal to that of the clock pulses, but also much higher, for example, 5 kc./ s.

Furthermore, the premagnetization of the core 11 which sets the same to a given rest condition need not necessarily be produced by the current lb through a winding 12 on the core 11, but may alternatively be brought about by a permanent magnet. The winding 12 and the gate 15 may then be dispensed with, so that the control signal is applied directly to the winding 13.

What is claimed is:

1. An electrical circuit arrangement for producing an output signal at a predetermined time interval following the initiation of an input control signal, comprising a saturable reactance element having a core of magnetic material with a rectangular hysteresis loop characteristic and first and second windings on said core, means for magnetizing the core to a predetermined flux value, means for applying a control signal to said first winding having an amplitude and polarity magnetizing the core to a second predetermined flux value, gate means for applying to said second winding signal pulses of given amplitude and duration to vary the magnetic flux of said core in a given number of incremental steps from the second predetermined value to the saturation value thereof, means for applying said control signal to said gate means to initiate the fiow of said pulse signal through said second Winding and initiate the said incremental changes of the flux of said core, and means responsive to the saturation of said core for deriving an output signal as determined by the pulse signal upon saturation of the said core.

2. An electrical circuit arrangement for producing an output signal at a predetermined time interval following the initiation of an input control signal, comprising a saturable reactance element having a core of magnetic material with a rectangular hysteresis loop characteristic and first and second windings on said core, means for magnetizing the core to a predetermined flux value, means for applying a control signal to said first winding having an amplitude and polarity substantially neutralizing the flux of said magnetizing means, gate means for applying to said second winding signal pulses of given amplitude and duration to vary the magnetic flux of said core in a given number of incremental steps from the said neutralized condition to the saturation value thereof, means for applying said control signal to said gate means to initiate the flow of said pulse signal through said second winding and initiate the said incremental changes of the flux of said core, and means responsive to the saturation of said core for deriving an output signal as determined by the pulse signal upon saturation of the said core.

3. An electrical circuit arrangement as claimed in claim 2 wherein said means responsive to the saturation of said core for deriving an output signal comprises an impedance element connected in series with said second winding and said gate and means coupled to said impedance for deriving said output signal.

it. An electrical circuit arrangement as claimed in claim 2 wherein said means for magnetizing the core to a predetermined fluX value comprises a third winding on said core and means for applying to said third winding a current having a value saturating the said core.

5. An electrical circuit arrangement as claimed in claim 4 wherein said means for applying a control signal to said first winding comprises gate means and further comprising means for actuating said gate means in response to said saturating current.

6. An electrical circuit arrangement as claimed in claim 5 wherein said saturating current and said control signal are in the form of pulses having a synchronous relationship.

7. An electrical circuit arrangement for producing an output signal at a predetermined time interval following the initiation of an input control signal, comprising a saturable reactance element having a core of magnetic material with a rectangular hysteresis loop characteristic and first, second and third windings on said core, current means coupled to said first winding for saturating the core in a given direction, first gate means for applying a control signal to said second Winding having an amplitude and polarity substantially neutralizing the saturation of said core, means for applying said saturating current to said first gate means thereby to actuate the same, second gate means for applying to said third winding signal pulses of given amplitude and duration to vary the magnetic flux of said core in a given number of incremental steps to the saturation value thereof, means for applying said control signal to said gate means to initiate the flow of said pulse signal through said third winding and initiate the said incremental changes of the flux of said core, and means responsive to the saturation of said core for deriving an output signal as determined by the pulse signal upon saturation of the said core, comprising an inductive element connected in series with said third winding and said second gate means.

References Cited by the Examiner UNITED STATES PATENTS 2,838,669 6/1958 Horsch 250-27 3,015,732 1/1962 Kuntzleman et al 307-88 3,062,440 11/1962 Kelly 235-92 BERNARD KONICK, Primary Examiner. S, M. URYNOWICZ, Assistant Examiner, 

1. AN ELECTRICAL CIRCUIT ARRANGEMENT FOR PRODUCING AN OUTPUT SIGNAL AT A PREDETERMINED TIME INTERVAL FOLLOWING THE INITIATION OF AN INPUT CONTROL SIGNAL, COMPRISING A SATURABLE REACTANCE ELEMENT HAVING A CORE OF MAGNETIC MATERIAL WITH A RECTANGULAR HYSTERISIS LOOP CHARACTERISTIC AND FIRST AND SECOND WINDINGS ON SAID CORE, MEANS FOR MAGNETIZING THE CORE TO A PREDETERMINED FLUX VALUE, MEANS FOR APPLYING A CONTROL SIGNAL TO SAID FIRST WINDING HAVING AND AMPLITUDE AND POLARITY MAGNETIZING THE CORE TO A SECOND PREDETERMINED FLUX VALUE, GATE MEANS FOR APPLYING TO SAID SECOND WINDING SIGNAL PULSES OF GIVEN AMPLITUDE AND DURATION TO VARY THE MAGNETIC FLUX OF SAID CORE IN A GIVEN NUMBER OF INCREMENTAL STEPS FROM THE SECOND PREDETERMINED VALUE TO THE SATURATION VALUE THEREOF, MEANS FOR APPLYING SAID CONTROL SIGNAL TO SAID GATE MEANS TO INITIATE THE FLOW OF SAID PULSE SIGNAL THROUGH SAID SECOND WINDING AND INITIATE THE SAID INCREMNTAL CHANGES OF THE FLUX OF SAID CORE, AND MEANS RESPONSIVE TO THE SATURATION OF SAID CORE FOR DERIVING AN OUTPUT SIGNAL AS DETERMINED BY THE PULSE SIGNAL UPON SATURATION OF THE SAID CORE. 